Previous maps of the relationship between branches of modern science were done by mapping the citations among journal articles. These citations are footnotes referencing previous articles on the same or related subjects. Citations are the equivalent links in a posting. They take you to the source. Citation indexes tally these links by subject. Mapping software can display the patterns of links. One example is below:
F. Schmid, and K. Richter. UbiGIS 2006 - Second International Workshop on Ubiquitous Geographical Information Services, (2006)Workshop at GIScience 2006.
F. Schmid. Seventh IEEE International Conference on Data Mining Workshops (ICDMW 2007), 0, page 655-660. IEEE Computer Society; Los Alamitos, CA, USA, (2007)